The present invention relates to a polycarbonate resin composition and more particularly to a polycarbonate resin composition comprising a polycarbonate resin and a siloxane compound and having excellent transparency and fluidity.
Thermoplastic resins, especially polycarbonate resins are used for a wide range of application because of their many advantageous properties such as high mechanical strength, impact strength, heat resistance, excellent electrical properties and transparency. These resins, however, have the disadvantage of being usually poor in moldability due to their high melting temperature and high viscosity in the molten state.
It is generally known to improve fluidity of polycarbonate resins by reducing their molecular weight, but this method involves the problem of adversely affecting the mechanical properties, particularly impact resistance of the resins.
Attempts have been made to blend various types of plasticizers or other resins for improving fluidity of polycarbonate resins.
For example, Japanese Patent Application Laid-Open (KOKAI) No. 55-18406 proposes blending of a cyclic siloxane compound, Japanese Patent Application Laid-Open (KOKAI) No. 54-100453 teaches addition of a siloxy-oxyalkylene block copolymer, Japanese Patent Application Laid-Open (KOKAI) No. 3-79626 discloses a method comprising copolymerization of the silicone chains to a polycarbonate, Japanese Patent Application Laid-Open (KOKAI) No. 3-84028 proposes a method using a polydimethylsiloxane-added isopropenylphenol as polycarbonate chain terminator, and Japanese Patent No. 3,090,764 discloses a method which comprises reacting a both-end epoxy-terminated organopolysiloxane and a polycarbonate. Any of these proposed methods, however, has its own problems, such as unsatisfactory effect, sacrifice in transparency, mechanical properties, heat resistance, etc., and expensiveness.
An object of the present invention is to provide a polycarbonate resin composition having excellent transparency and fluidity.
In the first aspect of the present invention, there is provided a polycarbonate resin composition comprising (A) 100 parts by weight of a polycarbonate resin and (B) 0.001 to 20 parts by weight of a siloxane compound which is a polyorganosiloxane having such a structure that at least (1) an aromatic hydrocarbon group, (2) an aliphatic or aromatic organic group having at least one carboxylic acid ester linkage, ether linkage or mixture thereof, and (3) a phosphorus atom-containing group, are bonded to the silicon atoms therein.
In the second aspect of the present invention, there is provided a polycarbonate resin composition comprising (A) 95 to 5 parts by weight of a polycarbonate resin, (C) 5 to 95 parts by weight of a styrene resin, and (B) a siloxane compound in an amount of 0.001 to 20 parts by weight to 100 parts by weight of (A) and (C) combined, said siloxane compound of (B) being the polyorganosiloxane as defined in the first aspect.
In the third aspect of the present invention, there is provided a polycarbonate resin composition comprising (A) 95 to 5 parts by weight of a polycarbonate resin, (D) S to 95 parts by weight of a polyester resin, and (B) a siloxane compound in an amount of 0.001 to 20 parts by weight to 100 parts by weight of (A) and (D) combined, said siloxane compound of (B) being the polyorganosiloxane as defined in the first aspect.
In the fourth aspect of the present invention, there is provided a polycarbonate resin composition comprising (A) 99.9 to 50 parts by weight of a polycarbonate resin, (E) 0.1 to 50 parts by weight of a copolyester resin comprising at least two kinds of dicarboxylic acids and a diol, with 1 to 50 mol % of said dicarboxylic acids being constituted by naphthalenedicarboxylic acid, and (B) a siloxane compound in an amount of 0.001 to 20 parts by weight to 100 parts by weight of (A) and (E) combined, said siloxane compound of (B) being the polyorganosiloxane as defined in the first aspect.